A vulnerability has been identified in Internet Explorer, which can be exploited by malicious people to display a fake URL in the address and status bars.

The vulnerability is caused due to an input validation error, which can be exploited by including the "%01" and "%00" URL encoded representations after the username and right before the "@" character in an URL.

Successful exploitation allows a malicious person to display an arbitrary FQDN (Fully Qualified Domain Name) in the address and status bars, which is different from the actual location of the page.

This can be exploited to trick users into divulging sensitive information or download and execute malware on their systems, because they trust the faked domain in the two bars.

Example displaying only "http://www.trusted_site.com" in the two bars when the real domain is "malicious_site.com":
http://www.trusted_site.com%01%00@malicious_site.com/malicious.html

A test is available at:
http://secunia.com/internet_explorer_address_bar_spoofing_test/

The vulnerability has been confirmed in version 6.0, and version 5.x is also affected according to Microsoft's knowledge base article.

NOTE: This vulnerability is currently being exploited on the Internet via scam emails!

Solution
Apply patches manually or via WindowsUpdate.
Further details available to Secunia VIM customers

Provided and/or discovered by
Originally discovered by:
Zap The Dingbat

Status bar variant reported by:
Chris Hall

Changelog
Further details available to Secunia VIM customers

Original Advisory
http://www.microsoft.com/technet/security/bulletin/MS04-004.asp

Other references
Further details available to Secunia VIM customers

Deep Links
Links available to Secunia VIM customers